This has to be very, very painful. Help is available but your daughter is too distressed to take it. She’s too old for you to have any authority and too young for you to have confidence that she will figure it out without getting into big trouble. It feels terrible to sit on the sidelines and wait for the inevitable.
All you can do directly is tell her that you love her; that you are worried for her; and that you are seeing signs that she is headed for trouble again. Emphasize that you aren’t judging her but that you want to help her catch the illness before she needs another hospitalization. Sympathize with how traumatizing the last episode was and about how hard it is to ask for help. As much as possible, it’s important to keep her in charge of what to do. When a person feels like their efforts to stay in control are slipping, the last thing the usually want is for someone else to take control away from them.
Your daughter’s clinicians can’t talk to you about her care unless she will sign a release. (It’s certainly worth asking her to do so but, since she is paranoid, it’s unlikely she will.) They can’t even confirm that she is their patient. But they can listen. You can call and tell them that you understand the limits of confidentiality but that you want them to know that the daughter you believe is their patient has stopped taking her meds and is anxious and paranoid. At least she is then on their radar. Since they know her, they will understand whether checking in with her would be a positive move or if it would make her more paranoid.
I also urge you to find a therapist for yourself, not because I think you are ill but because a professional can help you figure out what you can and can’t do. Further, you can then ask your daughter to join you in your therapy – which she might find less threatening than having you come into one of her sessions.
When a child is ill, the parent also suffers. I’m sorry that you are both going through this yet again.
I wish you both well.